When a car has a collision, the driver may collide with the steering wheel secondarily due to inertia. Thus, in order to protect drivers, a shock absorbing steering column apparatus has been widely employed.
In a shock absorbing steering column apparatus, when the driver has a secondary collision and the energy of the shock of the collision works from the rear part to the front part of the car, the steering column is disconnected from the car body to move to the front part of the car while being collapsed, and absorbs the shock energy meanwhile.
Generally, the steering column is supported and secured to the car body at two positions, that is, at an upper bracket in the rear part of the car and a lower bracket in the front part of the car.
The upper bracket in the rear part of the car of the steering column is provided with the shock absorbing mechanism described above. There is also provided a lock mechanism, etc., for tilt position adjustment and telescopic position adjustment.
On the other hand, the lower bracket in the front part of the car is provided with a supporting pin serving as the center of tilting movement so as to move the steering column in an inclined manner at the time of an operation for tilt position adjustment or telescopic position adjustment. At the same time, such a structure is also employed as smoothly disconnecting the steering column from the lower bracket when the steering column is collapsed to move to the front part of the car at the time of the secondary collision described above so as to securely guide the steering column to the front part of the car without dropping it downward. There is also a scheme for adjusting a telescopic position with an elongated hole which is provided on the lower bracket.
Incidentally, the upper bracket and the lower bracket described above are conventionally punched from one plate, and are manufactured through several steps.
However, since a blank is conventionally formed of one plate and bent several times repeatedly, it is inevitably necessary to bent the blank several times when a closed cross section is required. It is also necessary to weld the edges in alignment when more strength is required.
An area of the blank is required to be large for the bending process, so that a larger amount of metal is required than that actually used, and the fractional end portions are to be discarded. As a result, attention should be given to preparation of the blank in order to save waste to the utmost.